Write a Python program that prints the name of the longest DNA 
sequence in the file dna.txt in FASTA format. 

For example if the file contains 

>human
ACCGT
>mouse
AGTTATATA
>cat
AGT
>dog
GTGTATA

then the output should be 

>mouse


Your program should work for any number of sequences and not just the 
given example.

Submit a hardcopy in class on Sept 16th.